FiSBoG (Fetal Steroid Binding Glycoprotein) as a fetal functicn test

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MaureenE. DaltonaudCarlL.Mxose St. James'sUniversity Hospital,Leeds,England Abstract FiSBoGis a recentlydescribedfetalprotein. It can be detectedinthecordblood. It can be identifiedin matexnal serumin latepregnancy. In this studythevalues inmtemal serum in late pregnancyin 31 norm1 pregmncieswere cmpared with 23 abnormalpregnancies: 4 twin pregnancies, 4 stillbirth, 4 casesof pre-eclampsia, 4 who had a significant anteparturn haemrrhageand 7 who were m&l-for-dates, to assessits potentialas a test of fetalwell-being.FiSBcGappearedto have no significant role as a test of fetalwell-being. Introductican FiSBoGis a recentlvdescribedfetalorotein(1). It binds dihydrotestosterone (DKPi,testosterone and oestradiol with high affinity.Hcmever,unlikeSexHormoneBindingGlobulin(SBBG)it does not bind androstenedione or androstanediol. It may be relatedto OEl or 0E2 (2‘3)bn& is unlikelyto be relatedto Fetal SteroidBindingProtein(EEBI?) (4) as it bindsas a singlebinding site by Scatchardanalysisand it not detectablein non-pregnant adults. It is detectablein late pregmncy plasma. Elaterials and Methods Blocdwas takenfran 31 wcmen in latepregnancy(38 - 41 ~)and23klrmenwho~~o~1pregnancies:4~each withasignficantante~~~~~~ge (APH),4 stillbirth, 4 twinsand4pre-eclam&a, 7whoweremrethan2 S.D. belm weightfor gestationadjustedfor mternal heightand weight. The bloodwas centrifuged, separatedand frozen. The sampleswere then assay&d using a modification of the 'txotier c&mu' of IqbalandJohnson. Ammim sulphateprecipitation state is used initiallyto remve albumin, The precipitant was redissolved in tris buffer (pH 7) to the originalvolume. !l!hen 0.5 ml aliquots were inculxted with 3H DBJ!to give countsaround30,000cpn and then increasing amountsof 'cold'DKC, between0.1 to 4& t0 allm a five-point plot. These sampleswere incubatedfor 2 hoursand then 100 ul aliquotswere passedthrougha 0.5%ml colmtnof Cibacronblue F3GA Sepharose6B usinga 3rd cascadeof tris buffer. The Cibacronblue layerwas theh dissolvedin hnl of scintillation fluid,the radioactivity countedand a Scatchard plot perfomed. Only wheh there is a straightplot shming a high affinitybindingisit takenas FiSB&as residualalkxminmy also give a residualplot km of 1-r affinity. Resultsand Discussion FiSBcGwas undetectable in one thirdof materialfrun smples by4oweeks. F~~~~~~~p~c~s~~~,

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liltvariedfrcxn noxrral to raised. levelsin pre-eclampsia and SFD and fmn undetectable to raisedin stillbirths.These results suggestthat FiSE!&has no usefulrole as a test of fetal well-beingin latepregnancy. It acts ina similarwayto other fetalproteinssuch as alphafetoprotein (Fig.I).

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DaltonME (1984) Anotherfetalsteroidbindingglycoprotein, distinctfran !ZHEG.IRCSMsd Sci 1_2:743-744. Tomehave D, TeisnerB, ChenmitzJ and Westergaard JG (1987) InXnunacal studieson the tissuelocalisation of four antigensisolatedfran miotic fluid. -tracts ESHRE g:8. Fay T, TeisnerB, Bob H annd Grudzinskas JG (1987) Identification of -trial and 'new'fetalproteinin amnioticfluid. AbstractsESHRE 3_0:8. IqbalMJ, WilkinsonML and WilliamsR (1983) A non-circulating sex steroidbindingproteinin benignand ~~~t~~~s~e~d other malignancies.IRCS wd sci I_I:1125-1126.

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